Light microscopic histology of Achilles tendon ruptures - A comparison with unruptured tendons

We studied biopsies from the Achilles tendons of patients undergoing open r epair for a subcutaneous rupture of their Achilles tendons (27 men, 11 wome n; mean age, 45.3 +/- 13.8 years) and specimens of Achilles tendons from pe rsons with no known tendon ailments (43 men, 3 women; mean age, 64.2 +/-. 9 .7 years). Histologic examination was performed using stained slides that w ere interpreted using a semiquantitative grading scale assessing fiber stru cture and arrangement, rounding of the nuclei, regional variations in cellu larity, increased vascularity, decreased collagen stainability, hyalinizati on, and glycosaminoglycan. We gave up to three marks for each of these vari ables, with 0 being normal and 3 being maximally abnormal. All the histolog y slides were assessed twice in a blinded manner; the agreement between two readings ranged from 0.56 to 0.87 (kappa statistics). The score of rupture d tendons was significantly greater than the average score of control tendo ns (20.5 +/- 3.6 versus 6.5 +/- 2.1), and there was significantly higher de generation in the ruptured tendons. Nonruptured Achilles tendons, even at a n advanced age, and ruptured Achilles tendons are clearly part of two disti nct populations. Using these staining techniques, light microscopic degener ation is not a feature of tendons from healthy, older persons.